Hello All! I've been running water through 4" PVC with pots sitting in top of and the length of it in 3" holes. I have this beautiful brown slime growing inside the pipe. It's all over my roots, building up at the discharge holes. It is really nasty looking. I don't think it effects the plants alot but does help clog up the tubes clinging to the roots and pipes. my tomatoes are smaller than small marbles, I don't know what that's all about either.